1. Field of the Invention
The present invention relates to an automatic generation system for additional circuits provided in a logic circuit design support system. The present invention is advantageously used when changing the design of a logic circuit by including various additional circuits, for example, a reset circuit, a clock circuit, or a diagnostic circuit.
2. Description of the Related Art
In a logic circuit design support system, a computer is usually used to design and layout a logic circuit. In general, these processes are called "logic design" and "layout design".
In the logic and layout design processes, various additional circuits, for example, a reset circuit which generates a reset signal when initializing the logic circuit, a clock circuit which generates a clock for the logic circuit, and a diagnosis circuit for diagnosing the logic circuit by using a scan-out and scan-in operation, are automatically added to the logic circuit after completion of the basic logic design and the layout design. In general, these additional circuits are called "distributing additional circuits".
When automatically generating the additional circuits, it is necessary to determine points in which the additional circuits are to be connected in the logic circuit, and these points are grouped so as to satisfy various conditions of the logic circuit, for example, the limit for wiring length in the network and the number of fan-outs. The additional circuits must be connected so as to also satisfy the above conditions. After the above processes, the additional circuits are provided in the logic circuit.
In above processes, when the logic circuit is changed after completion of the basic logic design, it is necessary to change the additional circuits in accordance with above design change.